The production of alkenylbenzenes by the reaction of alkylbenzenes with conjugated dienes in the presence of an alkali metal catalyst is well known. These reactions, however, are carried out in catalyst slurries at moderate to elevated reaction temperatures. The alkali metal catalyst is slurried with the liquid alkylbenzene, and a conjugated diene is then added to the reaction mixture. See, for example, U.S. Pat. Nos. 3,766,288, 3,953,535, and 3,954,896, to Shima et al; U.S. Pat. Nos. 3,841,844, 3,865,889 and 3,904,702 to Mitchell; U.S. Pat. No. 1,934,123 to Hofmann et al.; U.S. Pat. No. 4,018,840 to Iwata et al.; and Teijin, Ltd. U.K. Pat. Nos. 1,390,874 and 1,483,426.
The prior methodologies have the disadvantage that often two or more alkenyl groups are added to the alkylbenzene because additional conjugated diene present continues to react with the initial reaction product. Moreover, the catalyst has to be recovered from the reaction mixture.
The method of the present invention overcomes this difficulty by separating the monoalkenylated benzene from the catalyst substantially as soon as it is produced, thus preferentially producing the monoalkenylated product at relatively high purity.